Response of dietary zinc and vitamin A levels on growth, immune response and carcass yield of broiler chickens

An experiment was undertaken to evaluate the response of broiler chicken to varying dietary levels of vitamin A and Zinc on the growth, immune response and carcass yield. A six weeks (0–6 weeks of age) feeding trial was conducted as per 3 x 4 factorial design involving three Zn levels (40,60 and 80 mg/kg) each with four vitamin A levels (1500, 3000, 6000 and 10,000IU/kg diet). Each of such test diet was offered as mash ad lib to four replicated groups of 8 chicks each. Significantly (P<0.01) higher body weight gain(BWG) was observed at 6000 IU/kg vitamin A than those observed at other dietary levels of vitamin A during all growth phases. The feed intake (FI) during 0–3 wk differed significantly (P<0.05) being higher at 40 and 80 mg Zn/kg diet than that recorded at 60 mg Zn/kg diet. The FI during 4–6 and 0–6 wks remained statistically similar either main effect or due to interaction effect between Zn and vitamin A. Significantly(P<0.01) lower and better FCR was observed at 6000 IU/kg vitamin A than those recorded at other dietary levels of vitamin A during 4–6 and 0–6 wk of age. The humoral (HA titer to sheep red blood cells- SRBC) was significantly (P<0.05) higher at 6000 and 3000 IU/kg vitamin A than those observed at other dietary vitamin A levels in the diets. Significantly (P<0.05) higher thymus weights was noticed at 60 and 80 mg Zn/kg diet than 40 mg Zn/kg diet. The various carcass quality traits and organ weights were not affected by different dietary treatments except percent shrinkage loss was increased linearly as increasing dietary Zn levels. The percent shrinkage loss was significantly (P<0.05) higher at 3000 and 6000 IU/kg vitamin A than those recorded at other dietary vitamin A levels. Based on the results it was concluded thata dietary level of 40 mg Zn/kg and Supplemental vitamin A 6000 IU/kg diet was found adequate to obtain optimum growth performance and carcass yield. However, better immune response was realized on dietary levels of Zn 60mg/kg and 3000 IU/kg vitamin A.